None.
The present invention relates to a concrete pump, and more particularly, to a system for detecting when air enters a concrete pump boom during a pumping stroke and controlling the operation of the concrete pump to minimize the effect of the air when it exits the boom.
Truck mounted concrete pumps are large concrete pumps carried on the frame of the truck. Truck mounted concrete pumps are used in a variety of large construction projects, including bridges, parking ramps, skyscrapers, and other types of multistory buildings. The concrete pumps comprise a hopper for receiving the concrete from a concrete supply source, such as a ready mix truck. From the hopper, the concrete is pumped through a boom system to a nozzle where the concrete exits the boom system. The boom system allows concrete to be delivered at significant distances from the hopper.
On the construction site, the operation of a truck mounted concrete pump typically involves several operators. A first operator monitors the supply of concrete from the ready mix truck to the hopper, a second operator controls the boom location and pump speed, and a third operator is positioned at the nozzle to control the application of the concrete. The first operator""s main responsibility is to ensure the hopper maintains a desired level of concrete. The first operator does this by controlling the speed at which concrete is fed from the ready mix truck into the hopper. For the pump to operate optimally, the concrete level in the hopper must be high enough to ensure that with each pumping stroke, the pump completely fills with concrete.
Should the operator become distracted, it is possible for the concrete level in the hopper to get too low, allowing a mixture of air and concrete to enter the pump. Once air enters the pump, an air pocket forms in the boom. Concrete is a nearly incompressible and highly viscous liquid so that as concrete continues to be pumped, the air pocket becomes compressed between the concrete entering the boom behind the air pocket and the concrete already in the boom ahead of the air pocket.
This compressed air pocket adversely affects the operation of the concrete pump. When the compressed air reaches the nozzle, it rapidly expands to atmospheric pressure, causing any concrete immediately in front of the air pocket to explode from the nozzle. This explosive spray of concrete not only splatters the concrete previously applied by the nozzle, but also causes the nozzle and boom to bounce and move around unpredictably and dangerously. If the operator located at the nozzle is unaware of the presence of the air pocket the operator may be knocked off balance by the movement of the boom. Any other personnel located near the nozzle must likewise use caution due to the unpredictable movement of the boom and uncontrolled burst of concrete from the nozzle.
In an effort to prevent the entrance of air into the boom, some contractors position two operators near the hopper to ensure the correct level of concrete remains in the hopper at all times. However, this greatly increases the cost associated with operating a concrete pump. Thus, there is a need in the art for a system to notify an operator that an air pocket is approaching in the boom pipeline, and there is a further need to minimize the explosive affect as the air pocket exits the boom.
The present invention provides a method of detecting the introduction of air into a concrete pumping system and further comprises a method of minimizing the nozzle and boom reaction when the air exits at the nozzle. The hydraulic pressure of the concrete pump is monitored to determine when a pump stroke contains air. As soon as air enters the boom system, an alarm notifies the operators of the pump that an air pocket is present in the boom. In addition, to minimize the effect the air pocket will have at the nozzle, the pump is controlled to slow the number of pumping strokes per minute as the air pocket approaches the exit of the concrete pump. By slowing the pump, the explosive effect created when the air pocket exits the boom is greatly minimized.